Method and apparatus for introducing samples into a gas chromatographic column



Jan. 27, 1970 R. s. TIMMINS ET 5 METHOD AND APPARATUS FOR INTRODUCING SAMPLES INTO A GAS CHHOMATOGRAPHIC COLUMN Filed May 10, 1968 SAMPLE INJECTION SYSTEM FIG. I

CARRIER COLUMN EEO TO COLUMN TO COLUMN CARRIER GAS F IG 4 TO COLUMN CARRIER GAS LEON MIR FREDERICK C. TOMPKINS BY I I W) F I O. 2

ATTORNEYS "United States Patent O Int. Cl. B01d /08 U.S. Cl. 55-67 10 Claims ABSTRACT OF THE DISCLOSURE Sample materials are vaporized for introduction into chromatographic columns by introducing the sample (liquid or solid) into a fluidized bed of heated particles, which provides substantially instantaneous vaporization of the sample. The carrier gas which fluidizes the particles, then sweeps the vaporized sample into the column.

This invention is directed to a method and apparatus for introducing gas samples into gas chromatographic columns. More particularly, the present invention relates to means for vaporizing a solid or liquid sample and introducing the thus-formed vapor into a gas chromatographic column in a non-diluted, plug-like or square wave form.

BACKGROUND OF THE INVENTION In gas chromatography, a sample of the mixture to be separated is introduced into a chromatographic column which is filled with a stationary phase of separatory material, such as an adsorbent in the case of a gas-solid chromatography or an inert solid coated with a liquid adsorbent in gas-liquid chromatography, i.e., crushed firebrick coated with a liquid adsorbing material. An axial coefficient of velocity is usually imparted to the gas sample mixture in the column by the introduction of an inert carrier gas. The stationary phase is chosen so that the different components of the sample mixture have different affinities for the adsorbent or absorbant material. Thus, different components of the sample mixture are retained by a column for a different length of time. As the band of sample mixture travels down the length of the column, the sample band gradually breaks into bands of the individual components. Complete separation of the components is obtained when the individual bands of each component no longer overlap in axial direction.

The gas sample should be introduced into the column in the form of a plug (i.e., with a top hat distribution or square wave form with a sharp back and frontal border). It is important that both the front and back borders of the plug are not diffused with the carrier gas. The more rapid and complete the vaporization, that is, the more closely the vaporized feed sample approximates the square wave, the better will be the resolution of the gas chromatographic column. An inefficiently vaporized feed will exhibit a tailing effect, that is, an overlapping of the successive bands with a resultant decrease in resolution. As the difficulty in the separation of the materials and/or the sample size increases, the problem of tailing increases.

Conventionally, liquid samples have been introduced into chromatographic columns by one of three methods. In the first method, a liquid is injected into a heated chamber (usually filled with solid metal spheres), placed in the carrier gas line to the column. Upon vaporization, the chamber is flushed with carrier gas to transport the vaporized sample into the column. The second method involves the injection of the liquid sample directly on top of the stationary phase in the chromatographic column with the column being continuously flushed with carrier gas to impart an axial coeflicient of velocity to the sample. In the third method, the sample is injected into a narrow chamber imbedded in a heated metal block. Upon vaporization, the chamber is swept with carrier gas to transport the vaporized sample into the column.

The above methods possess inherent deficiencies. For example, small tube heat exchangers tend to become fouled by decomposition and polymerization products as a result of the vaporization of the materials. The packed beds of the column also present a similar disadvantage in that liquid entrapment may occur at contact points with a subsequent bypassing of flow which increases the average residence time of the sample material and therefore the likelihood of phenomena such as decomposition or polymerization. In addition, there is a disadvantage of considerable temperature gradiants as a result of poor heat transfer within the apparatus and resulting uneven vaporization of the sample mixture which contributes to the aforementioned tailing.

Recently issued U.S. Patent No. 3,352,089, of Nov. 14, 1967 to Michael Model and James M. Ryan have provided means for vaporizing a liquid sample for introduction into a chromatographic column which comprises vaporizing the liquid sample in an empty vapor chamber and then flushing the thus-vaporized sample into the chromatographic column with the carrier gas.

A novel apparatus and method for introducing vaporized liquid samples to a chromatographic column has now been found which is not susceptible to the deficiencies of the prior art. This system is particularly applicable for the vaporization of large sample mixtures or for use in preparative or commercial gas chromatographic separations and systems where collection of samples is a prime objective.

SUMMARY OF THE INVENTION The novel apparatus of the present invention employs as an injection system a fluidized bed of particulate matter wherein the bed of particulate material is suspended in a chamber by the introduction of the carrier gas. The liquid or solid sample is then introduced into the fluidized bed, for example, by spraying, where it is vaporized and then swept by the carrier gas into the chromatographic column. Since the heating element involved, that is, the fluidized bed, remains in a violently agitated state throughout the course of the vaporization, and because of the heat of the bed and the large surface area of the particles, there is little, if any, opportunity for liquid entrapment at the contact points or any decomposition or polymerization resulting from the vaporization. In the fluidized bed, the temperature is substantially'uniform throughout the bed, thus eliminating the undesirable phenomena of uneven vaporization. Because of the rapid and even distribution of sample feed over the available heat transfer area and the short residence time in the fluidized 'bed and the resulting uniform vaporization, the desired square wave form behavior of vapor introduction into the chromatographic column is achieved.

DESCRIPTION OF THE DRAWINGS Turning now to the drawings wherein:

FIG. 1 shows a schematic representation of a typical gas chromatographic system employing the novel fluidized bed injection system of the present invention;

FIG. 2 shows an enlarged, partly schematic and sectional view of a one embodiment of the fluidized bed vaporizer within the scope of the present invention;

FIG. 3 shows an enlarged, partly schematic and sectional view of an alternative embodiment of the fluidized bed vaporizer within the scope of the present invention; and

FIG. 4 shows an enlarged, partly schematic and sectional view of still another embodiment of the fluidized bed vaporizer of the present invention.

FIG. 1 illustrates a gas chromatigraphic system of the present invention which includes a source of inert car ler gas 14, such as helium, nitrogen, argon, or the like; a source of the sample material 12 to be vaporized, which may be a liquid or solid, and a gas chromatographic columen which contains a bed of separat-ory material. The separatory material may be a particulate material. The separatory material may be a particulate solid, a solid coated with a liquid, resin particles, or even a gaspermeable gel. The novel system of the present invention is particularly directed toward liquid samples which are vaporizable, such as liquid hydrocarbons, solvents, solutions of solids, flavor essences, food extracts, and the like. Solids are also suitably treated by the fluidized bed injection system, particularly solids which sublime as well as those which pass through a liquid stage.

The fluidized bed injection system 16 is placed in fluid flow communication with carrier gas source 14 and sample source 12 and the top of column 10. Optionally, a timer or other responsive communicating system with the injection system is employed to provide the correct metering and valve operation of the sample system components. Means to detect the components emerging from the end of the chromatographic column are usually provided and identified as detector 15, such as a thermal conductivity cell, flame ionizing devices, or other detecting means. A collector 17 may be employed to collect the separate fractions of the sample material separated and emerging from chromatographic column 10.

FIG. 2 is a detailed View of the fluidized bed injection system 16 and includes a chamber 20 wherein a bed of particles 21 are fluidized by the introductin of carrier gas through inlet 23. The sample to be vaporized is introduced through a liquid sample feed 24 and sprayed into the bed through nozzle 25. Because of the heated bed, the large heating surface area of the particles and the violent agitation of the particles, the sample is almost instantaneously vaporized with a relatively short residence time in the chamber 20. After vaporization, the nowva-porized sample is carried to the chromatographic column by the carrier gas through conduit 28 in essentially a square wave form or plug.

FIG. 3 is a detailed view of an alternative injection system of the present invention which includes a chamber 20 containing a fluidized bed of particles 21 which is held suspended by the introduction of carrier gas through inlet 23. Screens 29 and 30 prevent the particulate matter from entering into the communication system with the chromatographic column or from falling into the carrier gas inlet system. Samples to be vaporized are introduced through liquid sample feed 24 which comprises a tube or conduit 24 which extends into the center of the chamber 20 and through the fluidized bed of particles 21. In order to introduce the sample material into the fluidized bed as rapidly as possible and thus achieve substantially instantaneous vaporization, a plurality of inlets 31 are located in the tube 24 to direct the sample into the heart of the bed thus maximizing the vaporization conditions.

The point of introduction of the carrier gas into the column is not critical; it is only necessary that the carrier gas be introduced at a point so that the pressure of the incoming carrier gas will be sufficient to maintain suspended within the column the bed of particles. The sample material may be introduced by any convenient means. For example, FIGURES 2 and 3 indicate two alternative methods of introducing the sample material. In addition, a plurality of points of introduction may be contained within the walls of the chamber 20. It is only necessary that the sample be introduced into the fluidized bed of heated particles to provide the desired vaporization. As indicated above, however, in connection with FIGURE 3, it is preferred that a plurality of points of introduction be employed in order to introduce the sample to the bed as rapidly and uniformly as possible to insure the most rapid vaporization possible, and thus the least amount of difiusion of the vaporized sample.

FIG. 4 is a detailed view of still another embodiment of the present invention wherein chamber 20 contains a heated bed of particles 21 fluidized by carrier gas through inlet 23. The sample 26 to be vaporized is introduced through conduit 24 into tube 32 located in the bed of fluidized particles. The heated particles are introduced into the lower end of tube 32 and the heat therein vaporizes the sample introduced into tube 32 by conduit 24. The particles exit tube 32 at the top and are reheated outside the tube. Thus there is a continuous flow of heated particles through the tube, and vaporization of the sample is accomplished with a minimum of dispersion.

The particulate matter employed in the column is not critical. It is only necessary that the particulate matter be heated sufi'iciently to provide for the vaporization of the particular sample involved. Preferably, high heat capacity materials are employed. As examples of suitable particulate material, mention may be made of glass, firebrick, polymeric materials, such as phenolics, polyolefins, such as polyethylene, metallic particles and hollow glass microspheres. The heat is imparted to the fluidized bed of particles by either external or internal heaters or by the gas stream used to fluidize the bed particles. If high heat capacity particulate matter is employed, once the initial heating has been provided to the column, very little additional heat is required to maintain the necessary temperature.

As examples ef suitable carrier gasses, mention may be made of steam, nitrogen, hydrogen, helium, methane, and argon.

If desired, the chromatographic system of the present invention may also include a bypass system to flow carrier gas into the chromatographic column without passing through the fluidized bed.

The fluidized bed injection system of the present invention can be employed with a series of chromatographic columns. By suitable valves and connecting means a sequence of the same or different samples can be vaporized and directed into a preselected sequence of chromatographic columns. In still another embodiment, a sample from a collector could be fed to a fluidized bed injection system for vaporization and injection into a subsequent column to provide still greater separation of materials.

The process of the present invention comprises, therefore, the introduction of a sample to be vaporized into a heated bed of particles which are fluidized in a chamber by the introduction of a carrier gas. The thus-vaporized sample, which may be a solid or a liquid, is then carried in a plug or square wave form into the top of the chromatographic column in essentially non-diluted form. The etfectiveness of the chromatographic system employing the fluidized bed injection system is indicated by the sharp delineation found between the separate fractions of the sample material which emerge from the column and are recovered in collector 17.

The novel apparatus and method of the present invention permits the introduction a vaporized sample into a relatively large chromatographic gas column in a highly concentrated vaporized, plug-like form and thereby avoids many of the difliculties and problems associated with prior processes in the art.

What is claimed is:

1. A gas chromatographic system which comprises:

a source of carrier gas;

a gas chromatographic column containing separatory material;

a means for introducing a sample gas into said column;

vaporizing means for providing said sample gas;

said vaporizing means comprising a chamber having connecting means to said chromatographic column;

a fluidized bed of particulate matter within said cham- ,7

her;

means for introducing carrier gas into said chamber;

said particulate matter being fluidized by said carrier means for introducing a sample to be vaporized into said chamber;

said particulate matter containing sufficient sensible heat to vaporize said sample.

2. The apparatus as defined in claim 1 wherein said means for introducing a sample into said chamber include means of spraying said sample into said chamber.

3. The apparatus as defined in claim 1 wherein said means for introducing a sample into said chamber include sample inlet means located within said fluidized bed.

4. The apparatus as defined in claim 3 wherein said inlet means include a plurality of openings in a conduit for introducing said sample into said fluidized bed.

5. The apparatus as defined in claim 1 wherein said sensible heat is provided by heaters external to said fluidized bed chamber.

6. The apparatus as defined in claim 1 wherein said particulate matter comprises hollow glass microspheres.

7. The apparatus as defined in claim 1 which includes screens adapted to retain said particulate matter in said chamber.

8. The apparatus as defined in claim 3 wherein said inlet means include a vertical tube having said particulate matter continuously passing therethrough.

9. A method for injecting a sample in vaporized form into a chromatographic column which comprises the steps of: (1) providing a bed of particles having sufficient sensible heat, to vaporize a sample material; (2) fluidizing said bed by introducing a carrier gas into said bed in suflicient, velocity to provide the fluidization; (3) introducing a sample to be vaporized into said bed whereby said sample is vaporized in said bed and swept from said bed into a chromatographic column by said carrier gas in nondiluted, concentrated, plug-like form.

10. A method as defined in claim 9 wherein said sample is introduced into said bed through a plurality ofinlets.

References Cited UNITED STATES PATENTS 3,225,521 12/1965 Burow -67 3,244,152 4/1966 MiXOn et a1 55-67 X 3,334,514 8/1967 Catravas 55-386 X 3,352,089 11/1967 Modell et a1. 55-67 3,389,538 6/1968 Carel 55-386 JAMES L. DE CESARE, Primary Examiner US. Cl. X.R. 55197 

